feat: add editing and MCP command handling, enhance SSE streaming with usage tracking

- Implemented `Edit` and `McpAdd` commands in the command parser and handler.
- Added a new `stream` module to the runtime for handling streaming events.
- Enhanced `SseParser` to parse usage information from SSE events.
- Introduced `ToolCallAccumulator` for tracking tool calls independently.
- Updated `AppStateRest` to include `app_config` and `MiscState` to track `effort_level` and `selected_index`.
- Modified `LlmClient` to support streaming responses with usage tracking.
- Improved error handling and retry logic in the streaming API calls.
- Added tests for new features and improved markdown rendering in the chat view.

src/app/state/misc.rs

@@ -204,6 +204,9 @@ pub struct MiscState {
     pub esc_press_count: u32,
     pub last_staleness_sweep_ms: i64,
     pub thinking: bool,
+    pub effort_level: usize,
+    pub selected_index: usize,
+    pub editor: Option<super::super::mode::editor::EditorState>,
 }
 
 impl MiscState {
@@ -216,6 +219,9 @@ impl MiscState {
             esc_press_count: 0,
             last_staleness_sweep_ms: 0,
             thinking: false,
+            effort_level: 1,
+            selected_index: 0,
+            editor: None,
         }
     }